1. Field of the Invention
This invention relates to the high speed weighing of pharmaceutical capsules and the like by checking differences in capacitance as each capsule is propelled between the plates of a capacitive transducer.
2. Description of the Prior Art
Capacitance gauging and weighing, of course, are not new. Gauging techniques of the capacitive type have been used in determining the thickness of various kinds of web stock. The mass of tobacco contained in cigarettes has been measured capacitively. See U.S. Pat. No. 3,979,581, granted on Sept. 7, 1976 to Joachin Revland, for instance.
Even pharmaceutical ingredients have been capacitively weighed. In this regard, U.S. Pat. No. 3,680,650, issued Aug. 1, 1972, to Robert W. Zimmerer, has used the capcitive concept for weighing a powdered pharmaceutical substance which is placed on a balance pan, the movement of a capacitance coupling plate associated with the pan relative to additional capacitor plates producing a signal representative of the weight of the substance. Whereas the weight sensing device in said patent could be utilized capsules, it would be a slow and tedious process and wholly unsuited for the rapid checking of such articles on a continuous and high speed basis.